1. Field of the Invention
The present invention relates to an apparatus for inserting a valve seat into a valve body and, more particularly, for inserting an annular, resilient valve seat into a butterfly valve body.
2. Description of the Background
Butterfly valves typically have an annular, resilient valve seat which is received in a valve body, the disk of the valve being mounted so as to form an interference fit with the valve seat. One such butterfly valve construction includes a valve body having a radially inwardly extending, annular rib which defines a generally circular bore through the valve body. The resilient valve seat has an annular web portion and two annular, radially outwardly extending flange portions which depend from opposite ends of the web portion and which form a radially outwardly opening, circumferentially extending channel, the channel having a cross-sectional shape which is complementary to the cross-sectional shape of the annular rib in the valve body. Accordingly, when the valve seat is received in the valve body, it is effectively mechanically locked to the valve body to prevent it from being dislodged when the valve is in service and under pressure. Butterfly valves of this type are shown, for example, in U.S. Pat. No. 2,994,342.
In valve seats such as disclosed in the aforesaid patent, insertion of the seat into the valve body is accomplished by manually folding the valve seat sufficiently to permit one of the flange portions to pass through the bore defined by the annular rib and then releasing the valve seat so that it returns to its normal configuration with the annular rib received in the channel.
In U.S. Pat. No. 4,685,611, there is disclosed a butterfly valve construction much as described above with the exception that the resilient valve seat contains a resilient, metal reinforcing member disposed internally of the resilient portion of the seat. Because of this reinforcing member, manual insertion of the valve seat into the valve body is difficult, though possible, because the reinforcing member tends to resist the folding necessary to distort the seat sufficiently so that one of the flange portions can be passed through the bore defined by the annular ribs. The problem is particularly acute with respect to small diameter valves wherein the reinforcing member renders the seat quite rigid and makes insertion difficult.